C433
On our 747-400s we don't have a specific LOC/BAC button on the MCP, but we are authorised to fly Localiser Back-course approaches.
From our Ops Manual:
Localiser Back Course Approach
If GPS is serviceable for the intended approach both pilots may display MAP and the localiser monitored using the localiser display on the PFD. For non-GPS aircraft the HP will display APP.
If the Back Course approach is not included in the FMS approach database, insert the ILS frequency and its front course QDM into the NAV RAD page, e.g. to fl the back course fro runway 25 at PHX insert 108.3/078.
Use LNAV or HDG SEL to track the localiser back course
T'bug